The present invention relates to a removable electrical or electronic equipment assembly which is of the type comprising a box or drawer and a housing capable of receiving the box and which is commonly called a "rack".
Installing an electronic box on board aircraft, helicopters or other vehicles presents more or less difficult problems of bulk, manipulation, positioning and then fastening or locking. The user wants to have systems allowing easy and rapid exchange, whilst at the same time remaining relatively robust and economical.
The extraction of a box from its housing can present problems, above all when it is heavy and the available space is limited. In fact, in addition to the weight to be overcome, it is usually necessary to exert considerable force for the plugging and unplugging of electrical connectors, especially since some box models have a large number of pins. There are also often seals for leakproofing or for mechanical protection or serving as an electromagnetic shield, which make it necessary to exert additional forces in order to insert or extract the box.
There are several systems for reducing the necessary forces: a handle with extracting cams, an articulated lever with a knurled nut, and a system comprising an endless screw and a rack. A system of this type, which is in common use, comprises, on the box, a lock support equipped with an endless screw driven in rotation by a shaft terminating in a machined hexagon intended for receiving an actuating tool. The housing intended for receiving the box possesses a rack which serves for interacting with the endless screw. This rack is connected to a slideway which guides the box when it is being inserted into or extracted from the housing. Furthermore, the box carries on its bottom, opposite the endless screw, a guide piece which interacts with the slideway.
In order to lock the box once it is in place, there are spring leaves which are fastened to the box and which penetrate into the notches of a gear wheel fixed to the endless screw. The form and arrangement of these springs are such that, when the tool is introduced in order to rotate the endless screw, the spring leaves are moved away from the said notches, thus allowing rotation to take place.
This system has some disadvantages, the most important of which arises as a result of the bulk of the component associated with the endless screw. This component penetrates inside the box and makes it complicated to provide the electrical or electronic equipment contained in this box, if a loss of space is to be avoided. Moreover, it is relatively heavy. In addition, the locking system formed by springs acting on a gear wheel can be distorted accidentally or as a result of the use of an unsuitable tool. Besides, the slideway integral with the rack constitutes an assembly which has to be machined with great accuracy and which is therefore relatively costly.